The present invention relates generally to query processing in relational databases and in particular to enhanced index access for intersect query processing.
Row identification (RID) list intersection is a common approach in query processing in relational database management systems (RDMS) such as IBM® DB2®, Oracle® Database, and Microsoft® SQL Server®. Currently, one method of RID list intersection is index anding. To apply a conjunction of predicates on a data table, a query processor performs index lookups to form one or more sorted RID lists (or bitmap) of the rows matching each predicate, merges all of the RID lists of matching RIDs for each predicate, intersects the RID lists via an AND-tree, and fetches the corresponding rows to apply any residual predicates. However, RID list intersection can become costly when the RID lists are large.